Low Blood Levels of Vitamin C Linked to Mortality

Laurie Barclay, MD

November 06, 2003

Nov. 6, 2003 -- Low blood level of vitamin C is strongly predictive of mortality, according to the results of a study published in the November issue of the American Journal of Clinical Nutrition.

"Older persons are at risk of both poor nutrition and increased oxidative stress," write Astrid E. Fletcher from the London School of Hygiene and Tropical Medicine in the U.K., and colleagues. "Plasma ascorbate concentrations fall with increasing age, and concentrations of other antioxidants may also be reduced."

In this add-on study to the Medical Research Council Trial of Assessment and Management of Older People in the Community, 1,214 persons aged 75 to 84 years randomly selected from the patient lists of 51 British family practitioners provided a blood sample and completed a food-frequency questionnaire. Median follow-up was 4.4 years.

Blood ascorbate concentrations were strongly inversely related to all-cause and cardiovascular disease mortality. These trends were only marginally reduced after adjustment for confounders or supplement use. Individuals in the lowest quintile for ascorbate concentration (<17 µmol/L) had the highest mortality, whereas those in the highest quintile (>66 µmol/L) had the lowest mortality (hazard ratio = 0.54; 95% confidence interval [CI], 0.34 - 0.84). After excluding subjects with cardiovascular disease or cancer at baseline, mortality for those in the highest quintile was still about half of that in the lowest quintile (hazard ratio = 0.51; 95% CI, 0.28 - 0.93).

Tocopherol, beta-carotene, and retinol levels did not predict total mortality, nor were dietary antioxidants measured by the food-frequency questionnaire associated with all-cause or cardiovascular disease mortality.

"A key question is how to increase concentrations of ascorbate in older age groups. Enthusiasm for vitamin supplementation has been tempered by the negative results from randomized trials, which were conducted predominantly in middle-aged populations," the authors write. "The best recommendation for older persons, as for middle-aged and younger persons, is to maintain a diet rich in a variety of antioxidant micronutrients. At older ages, however, several factors, such as reduced appetite and taste, poor dentition, physical and economic barriers to food sources, and lack of motivation, present formidable challenges to this strategy."

The European Union and the U.K. Medical Research Council and Department of Health helped support this study.

Am J Clin Nutr. 2003;78:999-1010

Reviewed by Gary D. Vogin, MD

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